The present invention broadly relates to a new and improved construction of a sealing shroud centrifugal or rotary pump, hereinafter simply referred to as a centrifugal pump.
Generally speaking, the sealing shroud centrifugal pump of the present invention comprises a pump housing and a sealing shroud sealingly separating the pump housing at its drive side against the action of the pumped medium. The wall of the sealing shroud protruding from the shroud base or bottom engages between an inner rotor and an outer rotor, each of which rotors are provided with permanent magnets. One of the rotors is connected with a pump impeller and the other rotor is connected with a drive motor.
Centrifugal pumps of the aforementioned type are known from Swiss Patent No 555,477 and German Patent Publication No. 2,620,502, published Nov. 25, 1976. They have, as is usual with sealing shroud pumps, an outer rotor connected to the drive motor and an inner rotor connected with the pump impeller. The pump impellers with their inner rotors are at least partly mounted on the base or bottom of the sealing shroud, and in the aforementioned German Patent Publication No. 2,620,502, the sealing shroud base or bottom has interruptions or apertures so that the so-called mounting or bearing shaft of the pump impeller can be mounted in a bearing in the shaft of the outer rotor.
Because of the prevailing requirements of mechanical power transmission, these prior known sealing shrouds are mostly made of metal and thus electrically conductive. This construction leads to the formation of eddy currents, corresponding heating and loss of efficiency. Up to now, plastic sealing shrouds have not been sufficiently chemically resistant or mechanically robust. Therefore, the prior art pump construction comprises many parts and is complicated.